Half of U.S. children and adolescents are overweight or at-risk for overweight. This is concerning because elevated BMI during childhood increases the risk of early onset of disease and disability in adulthood and reduced longevity. Mounting evidence demonstrates that weight also plays a significant role in interpersonal relationship formation. Weight appears to affect dating and sexual opportunities as well as engagement in sexual risk behaviors and reproductive outcomes. In particular, studies have demonstrated that being or perceiving oneself as overweight is associated with an increased risk of engagement in sexual risk behaviors. However, most studies utilize adult populations and cross sectional study designs and are therefore limited in their ability to identify the early precursors of these behaviors. Moreover, few studies have explored further downstream effects of weight on reproductive outcomes in adolescence or adulthood. Our recent research has contributed to the existing body of literature by demonstrating that the relationship between weight and sexual behaviors is evident as soon as during early and middle adolescence with significant racial variations. As rates of childhood obesity continue to rise, it is important that we develop a better understanding of how and for whom body size serves as a key contextual factor affecting adolescents'initiation and long-term perpetuation of sexual risk behaviors and reproductive outcomes. We propose to examine the relationship between adolescent weight, sexual behavior and reproductive outcomes by conducting secondary data analyses using two nationally representative longitudinal datasets: the National Longitudinal Survey of Youth 1997 (NLSY97) and the National Longitudinal Survey of Adolescent Health (Add Health). These complementary datasets follow school and non-school attending adolescents as they transition to early adulthood. We perform cluster analysis to identify subgroups of youth at highest risk for engaging in sexual risk behaviors based on their actual or perceived weight. We apply growth curve modeling techniques to identify longitudinal patterns of sexual behaviors and reproductive outcomes during the adolescent-to-adulthood transition, key predictors of these trajectories, and the effect of weight. We explore the effect of race and gender which few studies have examined. This proposal is innovative because we take a developmental approach to identify the mechanisms underlying the observed associations and identify subgroups of youth for whom these associations are strongest. This will allow us to identify individuals who may benefit most from targeted sexual health prevention programs. PUBLIC HEALTH RELEVANCE: Weight is an important contextual influence on sexual behavior. Being or perceiving oneself as overweight is associated with increased engagement in sexual risk behaviors and adverse reproductive outcomes. Little research has examined the relationship between weight, sexual behaviors and reproductive outcomes among adolescents which limits our ability to identify early precursors of these risk relationships. We conduct secondary data analyses using two nationally representative longitudinal datasets that follow individual from early adolescence through young adulthood to identify individuals who may benefit most from targeted sexual health prevention programs.